Radiological imaging is a major and increasing source of radiation exposure worldwide. Computed tomography (CT) is the largest contributor to medical radiation dose patients receive. Typically, CT scans impart doses to organs that are 100 times higher than doses imparted by other lower dose modalities such as chest X-rays. In general, CT examinations may involve doses (typically an average of 8 mSv) which may be equal to the dose received by several hundreds of chest X-rays (about 0.02 mSv/chest X-ray).

During an IAEA consultation on justification in 2007, it was estimated that up to 50% of examinations may not be necessary. It should be anticipated that part of the increase in global annual mean dose that has been observed recently is due to unjustified radiological procedures. Direct epidemiological data suggest that medical exposure to low doses of radiation even as low as 10-50 mSv might be associated with a small risk of cancer induction in the long term. The fact that a considerable percentage of people may undergo repeated high dose examinations , such as CT (sometimes exceeding 10 mSv per examination) dictates that caution should be used when referring a patient for radiological procedures. Health professionals need to make sure the patient benefits from the procedure and risk is kept minimal.

However, ensuring maximum benefit to risk ratio for the patient is not a trivial task. Referring medical practitioners, in a large part of the world, lack training in radiation protection and in risk estimation. 97% of practitioners who participated in a study underestimated the dose the patient would receive from diagnostic procedures. The average mean dose was about 6 times higher than the physicians had estimated. The fundamental principles of radiation protection in medicine are justification and optimization of radiological protection. Referring medical practitioners have a major role in justification. They are responsible in terms of weighing the benefit versus the risk of a given radiological procedure.

» What is justification and what is the framework?

Justification requires that the expected net benefit be positive. According to principles established by the International Commission on Radiological Protection (ICRP) and accepted by major international organizations, the principle of justification applies at three levels in the use of radiation in medicine.

At the first level, the use of radiation in medicine is accepted as doing more good than harm to the patient. This level of justification is now taken for granted. According to the revised International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources (BSS), generic justification of a radiological procedure shall be carried out by the health authority in conjunction with appropriate professional bodies, and shall be reviewed from time to time, with account taken of advances in knowledge and technological developments;
At the second level, a specified procedure with a specified objective is defined and justified (e.g., a CT examination for patients showing relevant symptoms, or a group of individuals at risk to a condition that can be detected and treated). The aim of the second level of justification is to judge whether the radiological procedure will usually Excellerate the diagnosis or treatment, or will provide necessary information about the exposed individuals. Professional bodies have prepared appropriateness criteria and recommend appropriateness of different radiological procedures in a variety of clinical conditions;
At the third level, the application of the procedure to an individual patient should be justified (i.e., the particular application should be judged to do more good than harm to the individual patient). At this level, the responsibility lies jointly with the referring medical practitioner and the radiological practitioner.

» Is the referring medical practitioner responsible for justification of radiological procedures?

Yes, jointly with the radiological practitioner. As stated above, justification at the third level is the responsibility of the referring medical practitioner, as is the awareness about appropriateness criteria for justification at level 2. According to the BSS, the radiological exposure has to be justified through consultation between the radiological medical practitioner and the referring medical practitioner, as appropriate, or be part of an approved health screening programme.

Since referring medical practitioners usually have the most complete picture of the patient’s health, they should be responsible for the guidance of the patient in undergoing only necessary procedures and benefitting from them. Particularly, this responsibility weighs more on generalists such as primary care providers. In order to facilitate justification in the case of radiological procedures, it is desirable that referring medical practitioners are knowledgeable about radiation effects in regard to the various dose ranges. The referring medical practitioners are responsible for keeping their knowledge about radiation up to date. In support of this, they should be provided education in radiation protection during their medical studies.

» How should justification be practiced and what knowledge is required for proper justification of a radiological procedure?

According to the BSS, the justification of medical exposure for an individual patient shall be carried out through consultation between the radiological medical practitioner and the referring medical practitioner, as appropriate, with account taken, in particular for patients who are pregnant or breast-feeding or paediatric, of:

The appropriateness of the request;
The urgency of the procedure;
The characteristics of the medical exposure;
The characteristics of the individual patient;
Relevant information from the patient’s previous radiological procedures.

Justification should be patient specific. The referring medical practitioner should take into account all clinical aspects regarding the management of every patient separately. Other possible procedures with lower or no exposure, such as ultrasound or magnetic resonance imaging, should be considered, if and when appropriate, before proceeding to radiological procedures.

» Is the acquisition of patients’ consent important?

According to the BSS, in order for a symptomatic or asymptomatic patient to undergo a medical procedure that involves ionizing radiation, the patient or the patient’s legally authorized representative should be informed in a timely and clear fashion, of the expected diagnostic or therapeutic benefits of the radiological procedure as well as the radiation risks. Thus, the emphasis is on provision of information.

» When is an investigation useful and what are the reasons that cause unnecessary use of radiation?

According to the guidelines published by the Royal College of Radiologists (RCR), a useful investigation is one in which the result, either positive or negative, will alter a patient’s management or add confidence to the clinician’s diagnosis. According to the RCR guidelines, there are some reasons that lead to wasteful use of radiation. With emphasis on avoiding unjustified irradiation of patients, the RCR report has provided a check list for physicians referring patients for diagnostic radiological procedures:

HAS IT BEEN DONE ALREADY? It is important to avoid repeating investigations which have already been performed relatively recently. Sometimes it is not possible to accurately track the procedures history of patients. Furthermore, patients may not be able to inform the practitioner that they had a similar procedure recently. It is important to attempt retrieving previous patient procedures and reports, or at least procedure history when possible. Digital data stored in electronic databases may help in that direction;
To help in avoiding repeating investigations, it is necessary to establish a tracking system for radiological examinations and patient dose. The IAEA has taken steps towards that direction by setting up the “IAEA Smart-Card” project;
DO I NEED IT? Performing investigations that are unlikely to produce useful results should be avoided, i.e. request procedures only if they will change patients’ management. It is important for the practitioner to be sure that the finding that the investigation yields is relevant to the case under study;
DO I NEED IT NOW? Investigating too quickly should be avoided. The referring medical practitioner should allow enough time to pass so that the disorder or impact of management of the disorder may be sufficiently evident;
IS THIS THE BEST EXAMINATION? Doing the examination without taking into consideration the optimal contributions of safety, resource utilization and diagnostic outcome should be prevented. Discussion with an imaging specialist may help referring medical practitioners decide on proper modality and technique;
HAVE I EXPLAINED THE PROBLEM? Failure to provide appropriate clinical information and address questions that the imaging investigation should answer should be avoided. Deficiencies here may lead to the wrong technique being used (e.g. the omission of an essential view);
ARE TOO MANY INVESTIGATIONS BEING PERFORMED? Over-investigating. Some clinicians tend to rely on investigations more than others. Some patients take comfort in being investigated.

» What are the reasons for over-investigating?

There are various reasons that may lead medical practitioners to refer patients for more procedures than needed. Practitioners should be aware of that and take action to avoid such situations. Some of the reasons that lead to over-investigation are the following:

Patient wishes. Patients feel more reassured when they are sure that their practitioner has thoroughly investigated their health condition. Some of them connect the quality of care with the number of procedures they undergo and ask their practitioner to subject them to more procedures. There must be a careful balance between informing patients of risks and benefits and the importance of considering patient desires and needs in the decision making process;
Financial. Some organizations or doctors get a direct financial benefit related to conflict of interest (also known as self-referral) from subjecting the patients to various procedures mainly because the services in question are provided by these health care professionals. Such practices are unethical and should not be accepted. Financial reasons may also influence a referring medical practitioner’s equity and also equal access to health services;
Defensive medicine. Some professionals rely far more heavily on investigations including radiological procedures than others, possibly to avoid litigation. In the case of radiological procedures, the risk should also be taken into account and exposure limited to the minimum required for a correct diagnosis;
Role of media. The opinion of the public on a subject is shaped by many parameters in a society. Media is one of them. For instance, exaggerated publicity in reporting a medical mistake may lead to increased public sensitivity about the subject. Publicity and increased sensitivity are good things and should be encouraged, but when reporting is not scientific but emotion-driven for audience reasons, as is often the case in mainstream media; this may lead to practitioners practicing defensive medicine and patients refusing indicated procedures; both of these scenarios undermine the appropriate practice of medicine;
Role of industry. The medical industry comprises large corporations that compete with each other for market-share. However, one large problem is that time is needed for new or improved technology, and this must be understood and assessed by the scientific community with regard to the cost-benefit ratio. Studies have to be done and sometimes results take time to come. This creates a window of time when misuse of equipment due to knowledge deficiency is possible;
Convenience. Sometimes a practitioner may subject a patient to a procedure that the patient has already undergone when imaging films or discs are unavailable, in order to save personal time, instead of checking the patient’s record. This is not relevant with the specific patient’s well-being, and similar convenience driven prescriptions should be avoided. Such practices are also unethical.

» Is there any guidance available?

During the last 20 years international and national organizations published guidelines for proper justification of radiological procedures. The UK Royal College of Radiologists (RCR) publication "Making the best use of clinical radiology services " has been in print since 1989. The American College of Radiology (ACR) published its guidelines as Appropriateness Criteria. Similar efforts have been undertaken by the Department of Health of Western Australia in Diagnostic Imaging Pathways.

For references of publications from national societies in Europe, Oceania, and other regions please see publication from Remedios. These publications constitute guidelines and aim to guide referring medical practitioners in the selection of the optimum procedure for a certain clinical problem. In case there are alternative procedures that do not utilize radiation but yield results of similar clinical value, these guidelines encourage the avoidance of radiological procedures.
The cited publications deliver very specific guidance to help practitioners perform justification properly.

» What is the role of radiation protection experts?

A medical physicist with experience and expertise in radiation protection will be able to provide information and guidance on radiation doses and risks in radiological procedures. In case you do not have an access to the help of radiation protection experts, referring medical practitioners may address their questions to their colleagues who work in radiology departments. However, staff specialized in radiation protection is more likely to provide complete, responsible and up-to-date information for the specific clinical problem. Radiation protection experts are comfortable with dose measurements and quantities which come from the domain of natural sciences and are usually hard to conceive for people outside the field.

» Which procedures are responsible for the highest doses to the patient?

The referring medical practitioner should be aware about procedures which impart high radiation dose to patients in order to be more cautious in such cases. This does not mean that other procedures should be written without proper justification. A quantitative knowledge of doses of various procedures is useful for the referring medical practitioner. Data given below will help the practitioner in that direction. In diagnostic radiological procedures, dose depends on the modality used. Computed tomography (CT) exposes patients to relatively high doses in comparison to other diagnostic imaging modalities.

Interventional diagnostic and therapeutic procedures that utilize fluoroscopy may also be a source of high radiation doses. Such procedures carry the risk of causing erythema to patients that receive high dose in single or repeated procedures. Some nuclear medicine procedures are also responsible for high radiation doses to patients.

» What if the patient whom I refer for a radiological procedure is pregnant?

The responsibility to identify patients that might be pregnant and are unaware of it is shared by the patient, referring medical practitioner and the imaging service providers. Safeguards to avoid inadvertent exposures of the foetus should be observed at all times.
The “ten day rule” was postulated by ICRP for women of reproductive age. The more latest “28-day rule” allows radiological procedures throughout the complete menstrual cycle unless there is a missed period. When a woman has a missed period, she is considered pregnant unless proven otherwise.

Even if safeguards are observed, sometimes a pregnant patient may be exposed to radiation. Depending on the radiation dose and the gestation age of the foetus, radiation effects may differ. Radiation risks are most significant during organogenesis in the early foetal period, somewhat less in the second trimester, and least in the third trimester.

As a rule of thumb one can assume that properly carried out diagnostic radiological procedures to any part of the body other than the pelvic region or when the primary X-ray beam is not passing through the foetus can be performed throughout pregnancy without significant foetal risk, if clinically necessary and justified. For radiological procedures where the primary beam intercepts the foetus, advice from the medical physicist should be obtained, who will calculate radiation dose to the foetus and, based on that, the practitioner and patient should make a decision. However, doses associated with radiotherapy procedures and interventional procedures are high and they require the attention of experts (including medical or health physicists, practitioners, and sometimes engineers and epidemiologists). In the case when a practitioner is responsible for a patient who has undergone a radiological procedure inadvertently and has subsequently been found to be pregnant, advice from the individuals listed above is needed. For more information, please click here where comprehensive information is provided not only for diagnostic radiology but also for nuclear medicine and radiotherapy.

» Should pregnant patients undergo radiological procedures?

Sometimes it is imperative that pregnant women should undergo radiological procedures. The referring medical practitioner and the imaging provider have to be mindful of risk and benefit and decide whether a radiological procedure should be asked for or if the medical problem may be solved by other non-radiological procedures. Generally, it is preferable that non-radiological procedures, or at least those that do not provide exposure to ionizing radiation, are used whenever possible. However, the use of radiological procedures is not prohibited and, when properly justified, they may be optimized so that these procedures may help to achieve the desired result for the patient while keeping dose to the foetus at low levels. The patient should be made aware about the possible impact of radiation exposure to the foetus. The need for consent must be determined based on individual practice standards, guided by more global professional or regulatory/legislative requirements.

» Can radiological procedures cause acute radiation injury?

Acute injuries such as skin erythema, blistering and hair loss have been recognized as a rare side effect of procedures guided by fluoroscopy. Similar injuries have been long recognized in radiation oncology, which uses much higher doses of radiation than diagnostic imaging. While radiation therapy is administered in fractions and the radiation-inflicted cells may recover in between sessions, fluoroscopy usually imparts a high dose to the skin in a short amount of time and with no dose fractionation. Referring medical practitioners could miss recognizing acute radiation injury resulting from interventional procedures. Such injuries may appear weeks after the interventional procedure and patients may not think of the procedure as being the cause unless they have been instructed accordingly by the interventional facility. Practitioners have often tended to attribute injury to many other causes, including insect bite and allergic reactions, but not to radiation exposure. Awareness about radiation through fluoroscopy being a possible cause can avoid mis-diagnosis and patient suffering.

Report of a consultation on justification of patient exposures in medical imaging. Rad. Prot. Dosimetry 135 (2009) 137–144.
Brenner, J.D., Doll, R., Goodhead, D.T., Hall, E.J., et al., Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know. P Natl Acad Sci USA 100 (24) (2003) 13761-13766.
Mettler, F.A., Huda, W., Yoshizumi, T.T., Mahadevappa, M., Effective doses in radiology and diagnostic nuclear medicine: A catalog. Radiology 248 (2008) 254-263.
Shiralkar, S., Rennie, A., Snow, M., Galland, R.B., Lewis, M.H., Gower-Thomas, K., Doctors’ knowledge of radiation exposure: questionnaire study. BMJ 327 (2003) 371–372.
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, 2007. Recommendations of the ICRP, Publication 103, Pergamon Press, Oxford (2007).
INTERNATIONAL ATOMIC ENERGY AGENCY. International Basic Safety Standards for protecting people and the environment. Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards. General Safety Requirements Part 3. No. GSR Part3 (Interim), IAEA, Vienna (2011).
Royal College of Radiologists. Making the best use of clinical radiology services. Referral guidelines. Sixth edition, London 2007.
Remedios, D., Justification: how to get referring physicians involved. Rad. Prot. Dosimetry (2011) Epub ahead of print, accessed 21 July 2011.

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